Many medical devices, for example, medical electrical leads and drug delivery catheters, include elongate bodies facilitating therapy delivery and/or diagnostic sensing; the bodies often include lumens extending along a longitudinal axis thereof. Such a lumen may provide a passageway for a stylet or guidewire that helps to guide the device to a target site within a body of a patient, for example, within a chamber of the heart. In recent years, the space used for guidewire/stylet lumens within elongate bodies of many medical devices has either been eliminated, to downsize the device bodies, or used for other purposes, for example, for the routing of one or more additional lead wires that add functionality to the device. Delivery devices, such as catheters, have been developed to guide these elongate medical devices, which do not have stylet/guidewire lumens, to a target implant site.
In order to implant the elongate body of a medical device in the venous system of a patient, for example, a right atrium, a right ventricle or a coronary sinus, an implanting physician may first obtain venous access by inserting an introducer sheath into an access site, for example, in the cephalic, sub-clavian, or axillary vein, according to methods known to those skilled in the art. The implanter may then pass a medical device into the venous system via insertion within a delivery catheter lumen, either before or after inserting the delivery catheter into the venous system through the introducer sheath. In some cases, the delivery catheter may also serve as the introducer sheath. Once the delivery catheter has been steered or directed to a target implant site within the venous system, the implanter may advance the medical device out through a distal opening of the lumen and then fix a distal end of the device at the site. After the medical device is fixed, the implanter may remove the introducer sheath and/or the catheter, from the venous system, by splitting a wall thereof to peel the sheath and/or catheter away from around a proximal portion of the medical device body that extends out from the venous system. This type of removal is desirable if the proximal portion, remaining outside the patient's venous system, is too large to fit within the delivery lumen of the sheath/catheter and/or if the implanter would prefer to maintain direct contact with the proximal portion of the implanted device while removing the sheath/catheter.
For many types of delivery catheters and introducer sheaths, a special slitting tool, that includes a cutting edge, is required to slit through a sidewall of the catheter/sheath, in order to remove the catheter/sheath from around the implanted device body. For those catheters and sheaths which have sidewalls constructed to provide kink resistance and adequate torque and push transfer, for steering the delivery catheter to the target site, slitting with these tools can be somewhat challenging. Even if a catheter/sheath sidewall is amenable to slitting, it may be difficult, particularly if the catheter/sheath is relatively long, to pull the catheter/sheath against the cutting edge of the slitting tool, along a relatively straight line in order to avoid a spiraling cut that could cause the peeling away of the sheath/catheter sidewall to dislodge the implanted device. Thus, there is a need for new delivery device constructions having kink-resistant sidewalls, that are sufficiently stiff to provide push and torque transfer, and that also include features to accommodate slitting.